Replace non-existent `gt mail ack` with `gt mail delete` in the witness role template. The `ack` subcommand exists in `bd mail` but not in `gt mail` - the correct command is `gt mail delete` which acknowledges and closes messages. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>